The present invention pertains generally to optical switches. More particularly, the present invention pertains to steering mirrors that are useful for routing light beams through free space. The present invention is particularly, but not exclusively, useful as an actuator for the steering mirror of an optical switch.
It has happened that optical components are being more and more frequently used in the manufacture of data transmission and communications systems. In most instances, these optical components include the use of optical fibers. Typically, these optical fibers have central cores that are made of an ultra-pure glass, and they include a cladding that surrounds the central core. Because the central cores have a higher refractive-index than that of the glass in the outer cladding, optical fibers are capable of conducting modulated light signals by total internal reflection. Further, these fibers can be used to manufacture optical fiber cables that consist of single or multiple cores, and have additional cladding and armoring for mechanical protection. In comparison with other types of signal conductors, the benefits that are obtained by using optical fibers include small diameters, high potential bandwidth and lower cost than more conventional conductors (e.g. copper wires).
Like all other types of communications systems, in order for an optical network to be effective, it must be operationally flexible. Stated differently, the optical system or network must be capable of being configured, and quickly reconfigured, with many different communications pathways. Clearly, this capability requires switches of some kind. In the particular case wherein the optical system incorporates optical fibers, the switches that are to be used must be able to direct a light beam from an end of a transmitting fiber to an end of a receiving fiber. Moreover, for the proper operation of the optical network, the switch may need to select a particular receiving fiber from a plurality of such fibers. Further, the switch may need to quickly redirect the light beam to another receiving fiber and, possibly, sequentially redirect the light beam to a plurality of receiving fibers.
Switches that mechanically align the ends of optical fibers with each other are typically limited in their performance by certain considerations that pertain in general to any type mechanical device. Specifically, these considerations include the fact that mechanical switches can be relatively slow in their operation. Further, due to corrosion and wear, mechanical switches are prone to losing precision in their alignments. Also, and perhaps more importantly, mechanical switches are susceptible to failure from material fatigue. In comparison, the degree to which these same imperfections may pertain to optical switches is much less significant.
It is known that mirrors can be effectively used for purposes of directing light beams on segmented beam paths through free space. Additionally, it is known that beam paths can be routed and rerouted by using only very small movements of a steering mirror. In the context of an optical switch, this fact can be very advantageous. Specifically, when mechanical operations can be limited to only those that are necessary for the proper orientation of a steering mirror, the extent and effect of these movements can be minimized. Accordingly, attention is then more appropriately focused on optical considerations for the optical switch. Included here are considerations of size. In particular, it is appreciated that many applications for optical switches require the switch be small and of minimal size. Insofar as the steering mirror of a switch is concerned, this means that the actuator for moving the mirror must also be small.
In light of the above, it is an object of the present invention to provide an actuator for moving the steering mirror of an optical switch that is compact in size and is, preferably, within the footprint of the mirror. Another object of the present invention is to provide an actuator for moving the steering mirror of an optical switch that is subjected to little, if any, material fatigue. Still another object of the present invention is to provide an actuator for moving the steering mirror of an optical switch that is relatively easy to manufacture, is simple to use and is relatively cost effective.
An actuator for moving a mirror, in accordance with the present invention, involves the interaction of electrical, magnetic and mechanical components. Importantly, operation of the actuator results in minimal, if any, material fatigue failure. Further, an important aspect of the present invention is that the actuator is dimensioned to define a footprint that lies completely within an area that is covered by the mirror. As contemplated for the present invention, the mirror will have a reflecting surface that is characterized by a largest dimension which is in a range approximately between one millimeter and twenty millimeters.
Structurally, the actuator of the present invention includes a base, and it has a rigid post that is mounted on the base to extend outwardly therefrom. A flexible connector is affixed to the end of the post that extends from the base. More specifically, this flexible connector is preferably made of an elastomeric material, such as silicone or rubber, which is capable of repetitively withstanding an extremely large number of cycles, while exhibiting substantially xe2x80x9czeroxe2x80x9d fatigue. Together, the post and the flexible connector establish a flexible universal pivot for the actuator.
An annular shaped permanent magnet is attached to the backside (non-reflective side) of the mirror, and is centered on the universal pivot around the permanent magnet. More specifically, the flexible connector is attached to the permanent magnet. With this connection the mirror is effectively mounted for pivotal movement on the flexible connector.
In addition to the structure mentioned above, the actuator of the present invention includes at least one electromagnetic device that can be controlled to tilt the mirror about an axis, while the mirror is attached to the flexible connector. Specifically, this electromagnetic device includes an electric coil that is mounted on the base. Also, the device includes a voltage source for sending a current through the coil. This is done to create a magnetic field that will interact with the magnetic field of the permanent magnet. Depending on the current that is sent through the coil, the electromagnetic device can control the magnetic interconnection between the permanent magnet that is mounted on the mirror and the electromagnetic device that is mounted on the base. Thus, the electromagnetic device can control the amount the mirror is tilted. Preferably, the actuator of the present invention will have two such electromagnetic devices that will cooperate with each other to tilt the mirror about orthogonal axes.
For the operation of the actuator of the present invention, an x-y-z coordinate system can be established wherein the mirror is moveable in rotation through an angle xcex8 around the x-axis, and in rotation through an angle xcfx86 around the y-axis. In this case, one of the electromagnetic devices is used to move the mirror through the angle xcex8 around the x-axis, and the other electromagnetic device is used to move the mirror through the angle xcfx86 around the y-axis. Preferably, the angle xcex8 is moveable through a range of xc2x110xc2x0 and, similarly, the angle xcfx86 is moveable through a range of xc2x110xc2x0. For an alternate embodiment of the present invention, the mirror may have a curved (spherical) surface and, further, the mirror can be moved in translation along the z-axis.